Interleukin (IL)-4 promotes class-switching of B cells from IgM to IgE and IgG. It is an important mediator of Type I hypersensitivity reactions following initial antigen exposure.
Anaphylaxis occurs quickly in severe Type I hypersensitivity reactions. Free antigen cross-links pre-formed IgE on mast cells and basophils, prompting the release of the vasoactive substances histamine, heparin, and eosinophil chemotactic factor A. Symptoms of anaphylaxis include systemic vasodilation, bronchial/tracheal constriction, and others.
Ozdemir reviews the T cell response to allergens. IL-4 and IL-13 are cytokines produced by Th2 cells and are responsible for class switching in B cells. This class switching results in production of allergen-specific IgE antibodies that bind to mast cells and basophils.
Arnold et al. review the management of anaphylaxis. Anaphylaxis causes dermatologic, respiratory, cardiovascular, gastrointestinal, and neurologic symptoms. Immediate administration of intramuscular epinephrine prior to respiratory or cardiovascular failure is essential.
Illustration A shows the signs and symptoms of anaphylaxis.
Answer 2: IL-5 is also responsible for B-cell class switching, but stimulates IgA production.
Answer 3: Interferon-gamma activates macrophages and Th1 cells.
Answer 4: IL-8 stimulates neutrophil chemotaxis.
Answer 5: IL-2 promotes the growth of cytotoxic T cells .
Ozdemir C, Akdis M, Akdis CA. T-cell response to allergens. Chem Immunol Allergy. 2010;95:22-44. Epub 2010 Jun 1. Review
PMID:20519880 (Link to Abstract)
Arnold JJ, Williams PM. Anaphylaxis: recognition and management. Am Fam Physician. 2011 Nov 15;84(10):1111-8. Review
PMID:22085665 (Link to Abstract)
USMLE World Step 1 Qbank Question #759. Copyright © USMLEWorld, LLC 2012